Re: std::vector : begin, end and insert - Using Objects instead of ints

"Nobody" <>
Wed, 11 Apr 2007 02:04:19 -0700

Question 1.
How do I get the integer value from _Iter

What integer value?

The one that is associated with the element.
I had that problem with "Pos" before.
I don't think I ever figured that one out either.

How do I use _Iter to get the object?


That fails, because I believe the iterator it is not an int. It is a CPoint.
I can't seem to define an interator as an int.
I have to define it as a CPoint.
std::vector<CPoint>::iterator m_Iter;

Would there ever be a difference between them?

Yes, there's no guarantee that an iterator is an index or a pointer;

I would like to know when?
I suppose it is just a fail safe.

... and has come out unreadable for me.

I have no idea why it did that. I may have pasted too much code.
I copy and paste from editor to Notepad,
then copy and paste again for the formatting.
It looked correct when I sent it.
I will just post a small portion relevant to the conversation.

P.S. The posted code will fail at your suggestion.

 std::vector<CPoint> m_Pts;

 CPoint Pt(2, 4);

 //--------------------------------------------------------------------------------- // Fill Collection //--------------------------------------------------------------------------------- for (UINT i = 1; i < 11; i++) { CPoint Pt; Pt.x = i; Pt.y = i; m_Pts.push_back(Pt); } //--------------------------------------------------------------------------------- // at : Returns a reference to the element at a specified location in thevector. //--------------------------------------------------------------------------------- for (UINT i = 0; i < 10; i++) { CPoint& rPt =; TRACE("Pt[%d] Pt.x %d, Pt.y %d\n", i, rPt.x, rPt.y); } //--------------------------------------------------------------------------------- // begin : A random-access iterator addressing the first element in thevector or // to the location succeeding an empty vector. You should alwayscompare // the value returned with vector::end to ensure it is valid. // // end : A random-access iterator to the end of the vector object. Youshould // compare the value returned to vector::begin to ensure it is valid. // //--------------------------------------------------------------------------------- m_Pts.resize(20); std::vector<CPoint>::const_iterator m_cIter; // *c1_cIter = 200; Error. c1_cIter is constant. m_cIter = m_Pts.begin(); TRACE("Position of Iterator: %d\n", *m_cIter); std::vector<CPoint>::iterator m_Iter; m_Iter = m_Pts.begin(); TRACE("Position of Iterator: %d\n", *m_Iter); m_Iter = m_Pts.end(); TRACE("Position of Iterator: %d\n", *m_Iter); *m_Iter = 10; TRACE("Position of Iterator: %d\n", *m_Iter); for (UINT i = 0; i < m_Pts.size(); i++) { CPoint& rPt =; TRACE("Pt[%d] Pt.x %d, Pt.y %d\n", i, rPt.x, rPt.y); } for(m_Iter = m_Pts.begin(); m_Iter < m_Pts.end(); m_Iter++) { CPoint& pt =*m_Iter); TRACE("Pt[%d] Pt.x %d, Pt.y %d\n", pt.x, pt.y); }

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